PuRNELL. — On tlie Wanganui Tertiaries. 453 



no distant date. The moa must have "wandered on the banks of the great 

 Cook Strait River, and the Apteryx and weka have hid in the forest which 

 covered the neighbouring plains. 



The previous existence of the moa in both islands is conclusive evidence of 

 the former continuity of the land, and that being proved it follows, as a matter 

 of course, that there was a Cook Strait Eiver, and that Port Nicholson was a 

 fresh-water lake. 



Art. LXXII. — On the Wanganui Tertiaries. By C. W. Purnell. 

 [Read before the Wellington Philosophical Society, 8th Augmt, 1874.] 



The Wanganui tertiary beds, or the " Wanganui Formation," as they are 

 called, have already been described by Mr. Buchanan and other competent 

 observers, and there being, so far as I am aware, no great geological problem 

 dependent upon their further examination, another paper on the subject may 

 by some be deemed superfluous. Original observations of physical phenomena 

 always possess, however, a certain value, and as I have lately been enabled to 

 make a personal survey of the tertiaries in the neighbourhood of the town of 

 Wanganui, I determined to put the results of my observations on record. 



The characteristic stratum of the Wanganui formation is the blue clay, the 

 development of which is best seen at Shakespeare Cliff, opposite the town of 

 Wanganui, where a thickness of forty feet is displayed. It is composed of a 

 fine greyish blue mud, shown by the fossils which it contains to have been 

 deposited in water of a moderate depth, and probably at the mouth of a river 

 or the outlet of a lake. It is important to notice that it was deposited in a 

 tranquil sea, and which must have remained quiescent for a considerable period 

 to allow of the rich accumulation of fossil shells of which the clay forms the 

 storehouse. A fine oyster bed is conspicuous in the lower part of the stratum, 

 and from top to bottom Ostrea, Pecten, Turritella, Murex, Terehratella, 

 AncUlaria, and many other sea shells abound, all being inhabitants of a coast 

 lying between low-water mark and a depth of 100 fathoms. Sharks' teeth and 

 a species of Bryozoa are scattered here and there. The oyster bed is, however, 

 so marked a feature of the stratum, while, moreover, beds of oysters and 

 Pectens exist in other strata of the same age in the district, that it would be 

 appropriate to call the blue clay and all the strata above it the " Wanganui 

 Oyster Beds," which name would be more descriptive than the somewhat 

 unmeaning term "Wanganui Formation." Shakespeare Cliff has been so 

 thoroughly ransacked by collectors that its fossils are well known, and the 

 only new shell I can offer is a species of Waldheimia which does not appear in 

 the Catalogue of the Tertiary MoUusca, issued by the Geological Department, 

 among the fossils of the Wanganui formation. 



